Fluid containers and especially flexible fluid containers for medical test systems often have problems associated with backflow of fluids that were previously introduced into the container. In one known way to avoid backflow, the container is held in a fixed position after fluid introduction to avoid reverse fluid flow. However, maintaining a fixed position is often problematic where the containers must be moved or otherwise manipulated, and/or where the container is flexible. In such case, undesired introduction of air may further complicate the process.
In another known way to avoid backflow, check valves can be used at the point of fluid introduction, and examples of known check valves are shown in Prior Art FIGS. 1-3. However, check valves often add substantial expense to the cost of the container and impose additional production steps in manufacture. Still further, most known commercially available check valves have a relatively large diameter, which typically interferes with tight packing or rolling of the containers, thus negating at least some of the advantages provided by flexible and flat test containers. To overcome some of these difficulties with known check valves, luer lock unidirectional duck bill valves can be used as described in WO07/120816. This and all other extrinsic materials discussed herein are incorporated by reference in their entirety, and it is noted that where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. While such duck bill valves tend to reduce the space requirements, they generally necessitate relatively large sample volumes as the luer lock of the valve matingly engages with a syringe and so creates a relatively large dead space.
Alternatively, dedicated custom made filling devices may be implemented to reduce problems associated with backflow. However, such filling devices tend to be expensive, and require at least in some cases maintenance and/or trained personnel. Furthermore, such filling devices typically require special fixturing and/or tooling for sample fluid introduction and the retention of fluids in the sample compartment.
In addition to backflow problems associated with currently known filling devices and structures, additional problems arise, especially where the container is flexible and/or where the fluid volume to be introduced is relatively small (e.g., less than 1000 μl). Among other problems, flexible containers are often subject to compression and thus at risk of valve failure. Moreover, the internal dead space of most of the currently known filling devices can be as large or even larger than the sample volume that is to be introduced, which renders sample application inaccurate at best.
Therefore, even though numerous containers with filling devices are known in the art, all or almost all of them suffer from one or more disadvantages. Consequently, there is still a need for containers with filling devices through which fluid can be introduced in a relatively small volume while eliminating backflow and leakage.